But CCIWA chief economist Rick Newnham said while WA was reaping the rewards of the GST deal, he shared the Treasurer's concern that the Budget revealed, over the long term, the state would see less of a return than first expected.

"There's many moving parts when it comes to the GST — the biggest moving part for WA is that the iron ore price has gone up," he said.

"When the iron ore price goes up our GST share goes down, but thanks to the GST deal our share is guaranteed at 70 cents in the dollar, which means that the amount of top up payments we receive this year is actually going up.

"But overall the GST pool is shrinking because people are spending less in the national economy, and that means that there's a significant risk now that our GST deal may be worth less over the longer term."

Mr Newnham said WA's GST return would decrease alongside the other states but that the impact of this would be buffered somewhat by the GST changes.

"The major moving part in the national economy for GST is consumption nationally, as people spend less in the national economy the GST pool for every state shrinks, and when it shrinks it means that states like WA get less in GST payments," he said.

"As the national spending slows, a lot of which has to do with house prices on the east coast, WA will receive less GST.

"Without the GST deal a shrinking GST pie would be a major issue, much more so than it is now, for WA."